Layered clay materials such as, for example, montmorillonite, hectorite, saponite and the like, are composed of silicate layers that have a thickness of about 1 to a few nanometers. Dispersions of such layered clay materials in polymers are frequently referred to as polymer-based nanocomposites.
Recently, there has been considerable interest in forming nanocomposites as a means to improve the mechanical properties of polymers. Specifically, nanocomposites of polymers have been shown to generally result in improved mechanical properties such as heat deflection temperature, modulus, tensile strength as well as fire retardancy.
U.S. Pat. No. 5,652,284 to Eidt, Jr., et al. (assigned to Exxon Research & Engineering Company) discloses a composite material that comprises an elastomer, from about 0.1 wt. % to about 15 wt. % of a layered mineral, and from about 0.1 wt. % to about 15 wt. % of asphalt; the aforesaid wt. % are based on the total weight of the composition. In the '284 patent, all three of the above components, i.e., the asphalt, elastomer, and layered clay mineral, are blended in melt, solution or in a mixer providing the disclosed elastomer-based nanocomposite composition.
The nanocomposite system disclosed in the Eidt patent contains the elastomer as the major component. Asphalt, on the other hand, is present in a relatively low amount, as compared with the elastomer, in this prior art nanocomposite system. Hence, the '284 (Eidt) patent discloses an elastomer-based nanocomposite, not an asphalt-based nanocomposite as is the subject of the present application. Asphalt-based nanocomposites differ from elastomeric-based nanocomposites in that in the former asphalt is present as the major component of the system. Asphalt molecules are the intercalating or exfoliating agent.